1. Field of the Invention
This invention relates to a plastic lens having a high refractive index with a low dispersion.
2. Description of the Prior Art
Recently plastic lenses have been widely used instead of inorganic glass lenses, because plastic lenses are more advantageous than inorganic glass lenses in the many properties such as lightness, safety, workability, dyeability, etc. For example, lenses made from diethylene glycol bisallyl carbonate (hereinafter referred to CR39) have been widely used. But, lenses made from CR39 have such a disadvantage that the lenses must be thicker than inorganic glass lenses, because of their relatively low refractive index such as 1.499. As the material for the plastic lenses with a high refractive index are known polystyrene or polycarbonate. However, they are considerably inferior to the polymer of CR39 in the superficial hardness, solvent resistance, weatherability, cutting-ability, dyeability, etc. Moreover, they have such a large dispersion that they are unfavorable as spectacle lens.
We have now found that the copolymer produced from polyfunctional allyl monomer and (meth) acrylate having an aromatic ring enables to produce a plastic lens having a low dispersion and a high refractive index, so that above-said drawbacks are dissolved.
An object of this invention is to provide a plastic lens having a high refractive index with a low dispersion.